This invention relates to the field of space structures. More particularly, the invention is oriented toward a structural joint concept for rapid assembly of truss stringers of large space structures. The potential use is in the construction of our nation's space station, contemplated and under development by the National Aeronautics and Space Administration.
There is a need for quick-erect truss structures that can be used in a variety of earth applications, as well as in space construction. These might be associated with towers that facilitate microwave and/or electrical power transmission and geodesic dome type architecture. In space, applications encompass the keel beam of the proposed space station, antennae masts, large platforms and solar energy truss support systems. These structures, both space and terrestrial, typically have a large number of joints, and a quick connect feature is mandatory to facilitate assembly in space at a single visit.
Other requirements of truss structural joints for use in space construction include a requirement that the joints be simple, inexpensive to fabricate, easy to inspect and easy to assemble by a space suited astronaut. A positive latching that will not loosen due to vibration or handling is required, and a direct structural load path through the joint so as to maximize both strength and stiffness is also requisite. The coupled joint should also have no external protrusion, and the unassembled member parts should be free of sharp or pointed edges, which could endanger the astronaut or puncture his pressure suit. The coupling joints planned to facilitate construction of a space station or other structurally redundant space frame require side entry attachment so as to provide removal of a single truss strut for repair and/or inspection without disassembly of additional pieces of the structure. It is also desirable to preload the joint axially to remove free-play and provide a linear load displacement response over a prescribed load range. Finally the optimum joint will be capable of any size application over a large range of large and small structural members.
A number of joints exist to couple struts in a truss structure, but none meet the plurality of requirements listed hereinabove.
Accordingly, it is an object of the present invention to provide a means of coupling tubular members such as struts or stringers that is easy to fabricate and which can be easily and quickly connected or disconnected.
Another object of the present invention is to provide a coupling means to join tubular members such as struts or stringers in a truss structure that is easy to construct and that has a minimum of moving parts.
A further object of the present invention is a means to join tubular members such as struts or stringers having positive latching that precludes loosening due to vibration or handling.
Yet another object of the present invention is to provide a coupling joint having a direct structural path co-linear with the centerline of the tubular members for maximum load bearing strength and stiffness.
Another object of the present invention is to provide a coupling means for tubular members such as struts or stringers that is free of sharp edges or protrusions, both coupled and unassembled, to protect space workers and facilitate packaging in a vehicle cargo bay.
Another object of the instant invention is a coupling joint for tubular members such as struts or stringers that permits side attachment and removal in a manner that allows removal of any single strut without disassembly of other pieces of the space truss structure.
Yet another object of the present invention is a coupling joint that when assembled does not have any axial free-play.
A further object of the present invention is to provide a coupling means for tubular members such as struts or stringers that can be preloaded with axial force to provide linear load-displacement response over a prescribed load range.
Yet another object of the present invention is to provide a joint capable of being fabricated for use with tubular members such as structural struts or stringers over a large range of sizes and load bearing capabilities.